.\" Copyright (c) 2005 Michael Kerrisk
.\" based on earlier work by faith@cs.unc.edu and
.\" Mike Battersby <mib@deakin.edu.au>
.\"
.\" %%%LICENSE_START(VERBATIM)
.\" Permission is granted to make and distribute verbatim copies of this
.\" manual provided the copyright notice and this permission notice are
.\" preserved on all copies.
.\"
.\" Permission is granted to copy and distribute modified versions of this
.\" manual under the conditions for verbatim copying, provided that the
.\" entire resulting derived work is distributed under the terms of a
.\" permission notice identical to this one.
.\"
.\" Since the Linux kernel and libraries are constantly changing, this
.\" manual page may be incorrect or out-of-date.  The author(s) assume no
.\" responsibility for errors or omissions, or for damages resulting from
.\" the use of the information contained herein.  The author(s) may not
.\" have taken the same level of care in the production of this manual,
.\" which is licensed free of charge, as they might when working
.\" professionally.
.\"
.\" Formatted or processed versions of this manual, if unaccompanied by
.\" the source, must acknowledge the copyright and authors of this work.
.\" %%%LICENSE_END
.\"
.\" 2005-09-15, mtk, Created new page by splitting off from sigaction.2
.\"
.TH SIGPENDING 2 2021-03-22 "Linux" "Linux Programmer's Manual"
.SH NAME
sigpending, rt_sigpending \- examine pending signals
.SH SYNOPSIS
.nf
.B #include <signal.h>
.PP
.BI "int sigpending(sigset_t *" set );
.fi
.PP
.RS -4
Feature Test Macro Requirements for glibc (see
.BR feature_test_macros (7)):
.RE
.PP
.BR sigpending ():
.nf
    _POSIX_C_SOURCE
.fi
.SH DESCRIPTION
.BR sigpending ()
returns the set of signals that are pending for delivery to the calling
thread (i.e., the signals which have been raised while blocked).
The mask of pending signals is returned in
.IR set .
.SH RETURN VALUE
.BR sigpending ()
returns 0 on success.
On failure, \-1 is returned and
.I errno
is set to indicate the error.
.SH ERRORS
.TP
.B EFAULT
.I set
points to memory which is not a valid part of the process address space.
.SH CONFORMING TO
POSIX.1-2001, POSIX.1-2008.
.SH NOTES
See
.BR sigsetops (3)
for details on manipulating signal sets.
.PP
If a signal is both blocked and has a disposition of "ignored", it is
.I not
added to the mask of pending signals when generated.
.PP
The set of signals that is pending for a thread
is the union of the set of signals that is pending for that thread
and the set of signals that is pending for the process as a whole; see
.BR signal (7).
.PP
A child created via
.BR fork (2)
initially has an empty pending signal set;
the pending signal set is preserved across an
.BR execve (2).
.\"
.SS C library/kernel differences
The original Linux system call was named
.BR sigpending ().
However, with the addition of real-time signals in Linux 2.2,
the fixed-size, 32-bit
.IR sigset_t
argument supported by that system call was no longer fit for purpose.
Consequently, a new system call,
.BR rt_sigpending (),
was added to support an enlarged
.IR sigset_t
type.
The new system call takes a second argument,
.IR "size_t sigsetsize" ,
which specifies the size in bytes of the signal set in
.IR set .
.\" This argument is currently required to be less than or equal to
.\" .IR sizeof(sigset_t)
.\" (or the error
.\" .B EINVAL
.\" results).
The glibc
.BR sigpending ()
wrapper function hides these details from us, transparently calling
.BR rt_sigpending ()
when the kernel provides it.
.\"
.SH BUGS
In versions of glibc up to and including 2.2.1,
there is a bug in the wrapper function for
.BR sigpending ()
which means that information about pending real-time signals
is not correctly returned.
.SH SEE ALSO
.BR kill (2),
.BR sigaction (2),
.BR signal (2),
.BR sigprocmask (2),
.BR sigsuspend (2),
.BR sigsetops (3),
.BR signal (7)
.SH COLOPHON
This page is part of release 5.13 of the Linux
.I man-pages
project.
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at
\%https://www.kernel.org/doc/man\-pages/.
